1. Field of the Invention
The present invention relates generally to exoskeleton systems that decrease the wearer's energy expenditure. More specifically, this invention describes an exoskeleton that, among other components, includes two hip actuators to power its leg supports and decreases the wearer's energy expenditure during the swing phase of the exoskeleton leg support. Since a person's oxygen consumption is related to the locomotion energy expenditure, the exoskeleton described here decreases a person's oxygen consumption when it is worn by the person for locomotion.
2. Discussion of the Prior Art
In a wide variety of situations, people of ordinary ability often consume a great deal of energy when walking or carrying a load. U.S. Patent Application Publication No. 2006/0260620 entitled “Lower Extremety Exoskeleton” filed on Apr. 1, 2009 and incorporated herein by reference, describes several embodiments of exoskeleton systems that allow their wearers to carry heavy loads. A paper entitled “The Effects of a Lower Body Exoskeleton Load Carriage Assistive Device on Oxygen Consumption and Kinematics During Walking With Loads,” K. N. Gregorczyk, J. P. Obusek, L. Hasselquist, J. M. Schiffman, C. K. Bensel, D. Gutekunst and P. Frykman, 25th Army Science Conference, Florida, USA, 2006, reports a set of experiments on an exoskeleton that was designed and built primarily based on U.S. Patent Application Publication No. 2006/0260620. The authors (all from Natick Soldier System Center) state that the exoskeleton that is built based on the '620 Publication increases the wearers' energy expenditure, although it increases the load carrying ability of its wearer. Another attempt to improve load carrying ability is set forth in the paper entitled “A QUASI-PASSIVE LEG EXOSKELETON FOR LOAD-CARRYING AUGMENTATION”, C. J. Walsh, K. Endo, and H. Herr, International Journal of Humanoid Robotics, 2007. However, the quasi-passive exoskeleton taught by Walsh et al. increases its wearer's oxygen consumption. More specifically, the exoskeleton described has no actuation and power unit and therefore will not be able to transfer power from the exoskeleton to the person. This means that this type of system, regardless of the location and strength of its springs, will not decrease its wearer's energy expenditure. Since oxygen consumption is proportional to energy expended, a wearer's oxygen consumption will not be decreased.
Based on the above, opportunities exist to provide a general purpose exoskeleton device which will decrease the wearer's energy consumption for locomotion while the device is worn. Providing an exoskeleton that decreases the locomotion energy consumption of its wearer would allow a wearer to walk and carry heavy objects while reducing the wearer's energy expenditure. In particular, this patent application describes several embodiments of exoskeleton devices that decrease their wearers' energy expenditure during swing phases.